The invention relates generally to electromechanical relays and, more particularly, to hermetically sealed electromechanical relays.
Hermetically sealed electromagnetic relays are sometimes used in explosive environments and/or for switching relatively high electrical currents and/or voltages. Hermetically sealed relays typically have stationary and movable contacts, and an actuating mechanism supported within a hermetically sealed chamber. High voltage, high current relays may suffer from contact welding and short circuiting of the relay terminals through vapor deposition of metal across the relay housing. These problems are caused by arcing between the moving contact and the stationary contacts, for example during hot switching operations. To suppress arcing, the relay chamber is evacuated and sealed so that the fixed and movable contacts coact in a complete or partial vacuum environment. Alternatively, the evacuated chamber is backfilled with an inert and/or insulating gas having good arc-suppressing properties. Further arc suppression may be achieved by imposing magnetic fields in the contact area. These magnetic fields cause a force on the arc column perpendicular to the current flow, which pushes the arc away from a source of plasma (hot arc spots) and stretches a length of the arc, thereby increasing the resistance to facilitate extinguishing the arc.
To hermetically seal the relay chamber, some known relays include an epoxy potting compound sealing an interface between the relay housing and a plastic holder that holds the stationary contacts. However, the epoxy potting compound may have a lower temperature rating than desired for some relay applications, which may compromise the hermetic seal above some temperatures. Moreover, some epoxy potting compounds may be porous to some gases, for example hydrogen, which may compromise the ability of the epoxy potting compound to hold a complete vacuum and/or contain some inert and/or insulating gases.
What is needed therefore is a hermetically sealed relay that contains a higher vacuum, has a seal that is less porous to some inert and/or insulating gases, and/or is able to maintain such a seal at higher temperatures than known hermetically sealed relays.